Alright, let's work through 81393001 times 99307945 step by step
81393001 × 99307945 = 99307945 × (81393001)
+ 99307945 × 1 resulting in 99307945
+ 99307945 × 00 yielding 0
+ 99307945 × 000 resulting in 0
+ 99307945 × 3000 that is equal 297923835000
+ 99307945 × 90000 yielding 8937715050000
+ 99307945 × 300000 giving us 29792383500000
+ 99307945 × 1000000 giving us 99307945000000
+ 99307945 × 80000000 producing 7944635600000000

= 8082971666692945
